Gauge question...

I'd like to make these mittens out of this yarn (that I got at this yarn store :) ).

Since the yarn is less chunky than the pattern calls for and I tend to be a loose knitter, I'm using size 6 needles instead of the 10.5s called for in the pattern. Which means that I need 18 stitches and 22 rows to get 4 inches square rather than 13 stitches and 19 rows.

I'm new to resizing stuff. Or even making stuff that has to actually fit a person. So if anybody (Queen of Socks?) wants to give some pointers, they'd be greatly appreciated.

I know I need to add extra stitches. I though about just going up to the men's pattern, but my stitch count(18) is 1.4 times greater than the specified gauge (13), and the men's pattern isn't proportionally that much larger than the women's. But maybe I'm not going about this right. Help?